In the absence of an efficacious vaccine and curative antiviral drugs against HIV-1, novel strategies are required to protect host CD4+ T-cells from the virus and curtail persistent infection. The overall goal of this application is to further develop nd characterize the inhibitory activity of cell-associated anti-HIV-1 monoclonal antibody (MAb) derivatives against HIV-1. Preliminary data indicate that targeting single-chain Fv (scFv) or the heavy chain third complementarity-determining region (CDR H3) of some anti-HIV-1 Env MAbs to lipid rafts with a glycosyl-phosphatidyl-inositol (GPI)-anchor enhances their potency as broadly neutralizing inhibitors of HIV-1 entry. Interestingly, both infection via cell-free virionsand cell-to-cell transfer are neutralized by the GPI- antibody derivatives. Additionally, oligomerizatin of an anti-HIV-1 Env GPI-CDR H3 further enhances neutralizing activity. We therefore hypothesize that GPI-anchored anti-HIV-1 antibody derivatives can potently neutralize HIV-1, thereby preventing infection of target cells and blocking viral replication. The hypothesis will be addressed in three specific aims. First, we will further characterize the mechanisms by which GPI-anchored antibody derivatives block HIV-1 replication. Second, we will characterize resistant viruses and identify specific escape mutations in envelope, and determine if coexpression of GPI-scFVs and GPI-CDR H3 enhances protection against infection by HIV-1 variants. Third, we will determine if ex vivo expanded HIV-1 specific T- cells from uninfected and HIV-1 infected individuals on HAART can be protected from viral infection by GPI- anchored antibody derivatives. Additionally, we will determine whether HIV-1-specific T-cells cells remain functional after transduction with GPI-anchored antibody derivatives. Successful completion of this project will demonstrate that GPI-anchored antibody derivatives with potent anti-HIV-1 neutralizing activity can protect virus-specific T-cells, thereby enhancing immune responses that may control or eradicate infection. This project brings together investigators with expertise in HIV virology, immunotherapy, and gene therapy in the U.S. and China to facilitate the development of novel gene therapy based HIV inhibitors. It therefore is within the goals of the U.S.-China Program for Biomedical Collaborative Research, RFA-AI-12-021.